Introduction

While there is a variety of common wisdom regarding the effects of mechanical advantage and friction on suspension lift lines, the only published charts I'd ever seen attempting to quantitatively illustrate the subject were speculative and presented conclusions seemingly defying the laws of physics.

I've finally had some time over the past few weeks to explore this issue in more depth, first developing a mathematical model of the system, and then performing some experimental measurements to test the predictions of the model and determine the relevant coefficients of frictions. What follows are my conclusions from that work.

Lifting Force

Let us imagine you are lifting a 100 lb bottom in a single-point suspension -- or, alternately, that you are lifting 100 lb worth of the body weight of a heavier bottom (for example, lifting their hips while their chest is...